Flash of Life at Conception: A team of scientists from Northwestern University have photographic documentation of the "flash of light" that occurs at the moment of fertilization. See that here:

5,200 Biologists Consensus at Fertilization: A University of Chicago study of biologists from over 1,000 institutions shows 95% of 5,500 biologists know that human life begins at fertilization. (The other 5% are so obsessed with dismembering unborn children that they lie about the most fundamental science in the own field of expertise. And the left, that cries scientific "consensus consensus" about matters with much less consensus, of course, hypocritically couldn't care less about this consensus.)

Preliminary Comment on Beginning of Biological Development: The Colorado Legislative Council has persisted in claiming against all scientific and medical research and common usage of English grammar that the phrase "the beginning of biological development," is "a term which is not defined… and is not an accepted medical or scientific term." So prior to presenting our answers to the council's thirteen questions, we're summarizing references that address this matter first, for both sexual (fertilization) and asexual (twinning, cloning, etc.) human reproduction.

THE BEGINNING OF BIOLOGICAL DEVELOPMENT

1.  SEXUAL HUMAN REPRODUCTION:

The following scientific references are provided by medical ethicist Dr. Prof. Dianne N. Irving of Georgetown University who herself writes herein, "Scientifically, the term 'embryo' as it refers to the sexually reproduced single-cell human embryo should apply from the biological beginning of that human organism, i.e., at the beginning of the process of fertilization or first contact of the sperm with the oocyte (as documented by Carnegie Stage 1)."

So, beginning this list of references with the widely influential Carnegie Stages of Early Human Embryonic Development: 

Carnegie Stage 1 Definition: Embryonic life commences with fertilization, and hence the beginning of that process may be taken as the point de depart of stage 1.  Despite the small size (ca. 0.1 mm) and weight (ca. 0.004 mg) of the organism at fertilization, the embryo is "schon ein individual-spezifischer Mensch"  (Blechschmidt, 1972). ... Fertilization is the procession of events that begins when a spermatozoon makes contact with an oocyte or its investments and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote (Brackett et al., 1972).  Fertilization sensu stricto involves the union of developmentally competent gametes realized in an appropriate environment to result in the formation of a viable embryo (Tesarik, 1986) ... .  Fertilization requires probably slightly longer than 24 hours in primates (Brackett et al., 1972).  In the case of human oocytes fertilized in vitro, pronuclei were formed within 11 hours of insemination (Edwards, 1972).  ... Fertilization, which takes place normally in the ampulla of the uterine tube, includes (a) contact of spermatozoa with the zona pellucida of an oocyte, penetration of one or more spermatozoa through the zona pellucida and the ooplasm, swelling of the spermatozoal head and extrusion of the second polar body, (b) the formation of the male and female pronuclei, and (c) the beginning of the first mitotic division, or cleavage, of the zygote.  ... The three phases (a, b, and c) referred to above will be included here under stage 1, the characteristic feature of which is unicellularity. ...  [see at cargnegiescience.edu from the Carnegie Stages of Early Human Embryonic Development, Stage 1.] (emphases added)

Human development is a continuous process that begins when an oocyte (ovum) from a female is fertilized by a sperm (or spermatozoon) from a male.  (p. 2);   ibid.: ... but the embryo begins to develop as soon as the oocyte is fertilized.  (p. 2);   ibid.:  [Single-cell human embryo]:  this cell results from the union of an oocyte and a sperm ...  is the beginning of a new human being (i.e., an embryo).  (p. 2);  ibid.:  Human development begins at fertilization, the process during which a male gamete or sperm ... unites with a female gamete or oocyte ... to form a single cell [embryo] .  This highly specialized, totipotent cell marks the beginning of each of us as a unique individual. (p. 18)  ...  The usual site of fertilization is the ampulla of the uterine tube [fallopian tube], its longest and widest part.  If the oocyte is not fertilized here, it slowly passes along the tube to the uterus, where it degenerates and is reabsorbed.  Although fertilization may occur in other parts of the tube, it does not occur in the uterus.  ... The embryo's chromosomes sex is determined at fertilization by the kind of sperm (X or Y) that fertilizes the ovum; hence it is the father rather than the mother whose gamete determines the sex of the embryo. [Keith Moore and T.V.N. Persaud, The Developing Human:  Clinically Oriented Embryology (6th ed. only) (Philadelphia:  W.B. Saunders Company, 1998), p. 37] (emphases added)

Human pregnancy begins with the fusion of an egg and a sperm. (p. 3);  ...  finally, the fertilized egg, now properly called an embryo, must make its way into the uterus  (p. 3);  ...   The sex of the future embryo is determined by the chromosomal complement of the spermatozoon ...  Through the mingling of maternal and paternal chromosomes, the [embryo] is a genetically unique product of chromosomal reassortment ... [Bruce M. Carlson, Human Embryology and Developmental Biology (St. Louis, MO:  Mosby, 1994), p. 31;  ibid, Carlson 1999, pp., 2, 23, 27, 32] (emphasis added)

In this text, we begin our description of the developing human with the formation and differentiation of the male and female sex cells or gametes, which will unite at fertilization to initiate the embryonic development of a new individual. ...  Fertilization takes place in the oviduct [not the uterus]... resulting in the formation of an [embryo] containing a single diploid nucleus.  Embryonic development is considered to begin at this point.  (p. 1);  ... [William J. Larsen, Human Embryology (New York: Churchill Livingstone, 1997), p. 17] (emphases added)

Fertilization is an important landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed.  (p. 5);   ibid.:  Fertilization is the procession of events that begins when a spermatozoon makes contact with a secondary oocyte or its investments ...  (p. 19);   ibid.: "The ill-defined and inaccurate term pre-embryo, which includes the embryonic disc, is said either to end with the appearance of the primitive streak or ... to include neurulation.  The term is not used in this book. [Ronan O'Rahilly and Fabiola Muller, Human Embryology & Teratology (New York:  Wiley-Liss, 1994), p. 55] (emphases added)

Advocating for Infanticide: Examples of public figures, ethics and religious authorities, student bodies, and leading media outlets, all of whom happen to be "pro-choice", despicably arguing for the decriminalization of killing children after they are born:

• • The Journal of Medical Ethics, After-birth abortion: why should the baby live, "...fetuses and newborns do not have the same moral status as actual persons... the authors argue that what we call 'after-birth abortion' (killing a newborn) should be permissible in all the cases where abortion is, including cases where the newborn is not disabled." -Alberto Giubilini and Francesca Minerva (Related: And if you can kill kids, why not also have sex with them, as the pro-choice Stephen Kershnar, chairman of the State University of New York, Fredonia philosophy department suggests.)
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• • The New York Times, Why They Kill Their Newborns, three page article advocating decriminalized infanticide by MIT's Stephen Pinker. ARTL Question: If they used a gun to kill the baby, do you think that more people would realize that it was wrong?

• • Philosophy & Public Affairs, Abortion and Infanticide, and online: "It will be seen that this condition is not satisfied by human fetuses and infants, and thus that they do not have a right to life." -University of Colorado professor Michael Tooley

• • Discover Magazine, The Evolution of Infanticide, "Infanticide is thus at one extreme in a spectrum of parental care." -Sarah Hrdy. Ideas have consequences and a life of their own.

• • The Guardian describes a non-judgmental French infanticide novel as "the darker side of maternal love" and quotes the translator: "It apportions no blame. ...you come out of it sympathising with her... It may not be an evil act; it may be... a misguided act of love." 
•  
• • Singer & Dawkins, the world's most notorious "bioethicist" and evolutionist, advocate killing handicapped children. The above sources defend the killing of any babies and to that end, Peter Singer is well known for claiming that "the life of a newborn baby is of less value than the life of a pig, a dog, of a chimpanzee." In this brief clip, speaking to Singer, Richard Dawkins, the world's leading promoter of Charles Darwin's theory of evolution, is limiting (currently) his defense of after-birth abortion to handicapped children, in his advocacy of infanticide:

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  Beyond Abortion: Those rebelling against God's command, Do not kill the innocent, are not satisfied with just the unborn. After decades of misguided pro-life effort to regulate child killing, ARTL's regulations teaching helps pro-lifers get back into the actual war. The opposition is now killing infants, handicapped children, and the elderly, exposing regulatory efforts based on heartbeats, waiting periods, and clinic regulations as utterly irrelevant.

• • Church of England backs killing severely disabled
  babies at birth, reported the Daily Mail in reaction
  to a paper two years in the making by the Bishop
  of Southwark, Tom Butler, vice chair of the Church
  of England's Mission and Public Affairs Council.

• • The Royal College of Obstetricians and Gynaecology,
  proposes "deliberate intervention" to kill handicapped
  babies after they are born, reports the BBC.
  "Withdrawing treatment [i.e., food and water] is
  already permitted..."

• • Drudge Headline: (see screenshot below) Shock Report:
  College students increasingly support 'post-birth abortion'.
   
• • UK Telegraph on J. of Med. Ethics: In a largely
  positive report, Killing babies no different from abortion, experts say, the Daily Telegraph quotes the journal’s editor, Prof Julian Savulescu, director of the Oxford Uehiro Centre for Practical Ethics, in a grotestquely ironic criticism of those enraged at the journal. "This 'debate' has been an example of 'witch ethics' - a group of people know who the witch is and seek to burn her. It is one of the most dangerous human tendencies we have. It leads to lynching and genocide. Rather than argue and engage, there is a drive is to silence and, in the extreme, kill, based on their own moral certainty." Advocacy of child killing, whether in or out of the womb, leads to a kind of moral insanity.
• • Huffington Post March 2015: A report on this very American RTL infanticide article refers to this concern as "hype". Sadly, this leftist news and opinion site criticizes our pro-life efforts to oppose such infanticide advocacy, but displays no moral outrage, nor even criticism, of any of those above advocating killing children.
• • UK Telegraph April 2015: In "Woman jailed for 'killing her foetus' - this is a sad day for us all", this popular British newspaper uses the term fetus for a South Bend, Indiana child whom the courts determined had been alive after it was born. The Telegraph report shows not the least interest in whether the cause of the baby's death occured before or after birth.

• • Denver's Children's Hospital, horrifically, advised the parents of four-year-old Dylan Walborn to euthanize their handicapped son. Authorities would jail someone who starved to death a horse or even a dog, but starving a boy? They call that compassion. Again, would more people realize this was wrong if they had used a bullet?

The abortion theater of war is so far removed from regulations like informed consent and waiting periods, that efforts in that direction are not only misguided. Regarding regulating child killing, worse than all that, is that these efforts remove troops from the actual battlefield. But even then, that's not the worst of it. Click to see what is actually the worst of it.

Hear this Colorado RTL radio spot warning about the growing advocacy of infanticide.